300 AAC SBR Upper questions - thoughts

[MemHeli]

Does anyone have experience with this upper?

 

 http://www.cdnnsports.com/email-specials-html/ar15-custom-pistol-upper-300aac.html#.VmCxu4RZvek

 

I've been looking at it for an SBR.  Really just getting started in my research, but I know I want to build a SBR in 300AAC.

 

 

[JeffL]

No experience here, but that's good price.

[Hozzie]

Only issue you may have is if you want to shoot subsonics.  I would want a 1/7 twist for the heavy bullets.  If not, it will be fine.

[MemHeli]

The price does seem good!  I definitely want to shoot subsonic!  So this one is too many twist for that heavy bullet.  Makes sense.

[Hozzie]

It may or may not stabilize certain bullets. Only way you will know is to shoot it. I doubt it will stabilize a 200 grain or higher, but it might. If you can find a load for a 180-190 grain bullet it would have a better chance. Edited December 3, 2015 by Hozzie

[btq96r]

I'm no expert on the proper twist for subsonic .300BLK, especially with a can on the end.  Dolo would be the one to get into this thread for that.  I'll be lurking to see what comes from him or others as a .300BLK upper for my SBR is on the shopping list when I can set aside enough for a can.

 

For what you linked though, despite not getting a commission from it, I'll shill for Primary Arms here and ask you to look at this if 1:8 twist is good to go:

http://www.primaryarms.com/radical-firearms-85-300blk-quad-rail-upper-receiver-without-bcg-or-charging-handle/p/kt-rfupperv1.0.85-300/

Edited December 3, 2015 by btq96r

[Alleycat72]

It may or may not stabilize certain bullets. Only way you will know is to shoot it. I doubt it will stabilize a 200 grain or higher, but it might. If you can find a load for a 180-190 grain bullet it would have a better chance.

What? I've been shooting 240, 250, and 260s in a 1 in 8 for 10 years.

[Hozzie]

What? I've been shooting 240, 250, and 260s in a 1 in 8 for 10 years.

In a 300 Blackout SBR? I have a 8.5" 1/7 McGowen barreled 300 Blackout and 240s will stabilize, but I don't think they will in 1/8. It's not an exact science. Each bullet will be a bit different depending on their design.

No one can say for sure what will stabilize without testing and you have to test before putting the suppressor on.

If you like the price, go for it. You can find some bullet that will work, but heavier bullets are easier to get subsonic. To be fair, my barrel was $350 so I don't think you would ever lose money even if you get it and find out you want a higher twist. Edited December 3, 2015 by Hozzie

[hipower]

No experience with the 300 BO, but commenting on price here.

Have you checked the Palmetto State Armory pricing on uppers?

[Alleycat72]

In a 300 Blackout SBR? I have a 8.5" 1/7 McGowen barreled 300 Blackout and 240s will stabilize, but I don't think they will in 1/8. It's not an exact science. Each bullet will be a bit different depending on their design.

No one can say for sure what will stabilize without testing and you have to test before putting the suppressor on.

If you like the price, go for it. You can find some bullet that will work, but heavier bullets are easier to get subsonic. To be fair, my barrel was $350 so I don't think you would ever lose money even if you get it and find out you want a higher twist.

It's a 10.5 sbr. I've had a 16" SSK Whisper for ever. It's a 1 in 8 also.

[Alleycat72]

[Jct1911]

What? I've been shooting 240, 250, and 260s in a 1 in 8 for 10 years.

Not 10 but 3 in my case. Had both 1/8 and 1/7. Zero issues with stability with many different bullet designs.

OP,
I think the upper is a crap shoot at best. Cdnn bought a bunch of leftover LWRC rails and have been throwing them on every kind of upper they can. I think it's a tad deceitful, going for name recognition with the handguards and then cheap parts everywhere else. I'd pass and buy from well known supplier of quality AR's. Or build as I do.

This is a 10" 1/8 lothar-walther lw50 on mega receivers , Griffon Armament taper mount on end for form 1 suppressor
Edited December 4, 2015 by Jct1911

[Lumber_Jack]

I have a 10.5 1:8 twist and it stabilizes 220gr no problem.

[MemHeli]

Not 10 but 3 in my case. Had both 1/8 and 1/7. Zero issues with stability with many different bullet designs.

OP,
I think the upper is a crap shoot at best. Cdnn bought a bunch of leftover LWRC rails and have been throwing them on every kind of upper they can. I think it's a tad deceitful, going for name recognition with the handguards and then cheap parts everywhere else. I'd pass and buy from well known supplier of quality AR's. Or build as I do.
 

I see what you're saying about all the LWRC rails, and that is what caught my eye at first.  I'm going to call them and see if they can tell me what manufacturer the barrel is.  I would not mind building one from ground up...just no experience or tools.  I have plenty of tools, just not specific to building AR's.  Been eyeing that Magpul wrench though.  It looks beefy.

[MemHeli]

I'm no expert on the proper twist for subsonic .300BLK, especially with a can on the end.  Dolo would be the one to get into this thread for that.  I'll be lurking to see what comes from him or others as a .300BLK upper for my SBR is on the shopping list when I can set aside enough for a can.

 

For what you linked though, despite not getting a commission from it, I'll shill for Primary Arms here and ask you to look at this if 1:8 twist is good to go:

http://www.primaryarms.com/radical-firearms-85-300blk-quad-rail-upper-receiver-without-bcg-or-charging-handle/p/kt-rfupperv1.0.85-300/

ok, so I notice on the CDNN model, the top rail is removable allowing access to the gas system.  Why is this important.  Can it not be cleaned without breaking down otherwise?  

The Button Rifled barrel type is a new one for me.  Just read that this is a progressive cutting method, removing a little more metal with each pass.  The CDNN model does not mention rifling method.  I'll ask about that as well when I call.

[Hozzie]

Ok, I have to eat a bunch of Crow.  I have no excuses as much as I wish I did.  :surrender:

 

I had to go back and look at my upper and see if I had misspoke.  Of course with my rail on I couldn't see the twist rate, but when I looked up my order, there it is in black and white.

 

3003080820SS 30 Caliber 1-8" Twist, 20" SS Blanks 1

AR15 Pre-Fit 300 Blackout, Modified HBAR, .750" Gas, Pistol Length Gas

System, 8.5" Long, 5/8" x 24 TPI

 

I think I had stuck in my head my research between 1/7 and 1/8 on some AR's.  I know my old Sig 556 had a 1/7 twist which was for heavier bullets.  So mea culpa, I was wrong.

 

Sorry about that.  That's what I get for not checking first to make sure.  So, for that kind of money, I don't think you can go wrong.  I agree it won't be the highest quality, but it will probably work just fine.  Building one is always fun and a good learning experience though.  I just ordered some items to build a 5.56 upper to put on mine as well.

Edited December 4, 2015 by Hozzie

[Lumber_Jack]

Ok, I have to eat a bunch of Crow.  I have no excuses as much as I wish I did.  :surrender:

 

I had to go back and look at my upper and see if I had misspoke.  Of course with my rail on I couldn't see the twist rate, but when I looked up my order, there it is in black and white.

 

3003080820SS 30 Caliber 1-8" Twist, 20" SS Blanks 1

AR15 Pre-Fit 300 Blackout, Modified HBAR, .750" Gas, Pistol Length Gas

System, 8.5" Long, 5/8" x 24 TPI

 

I think I had stuck in my head my research between 1/7 and 1/8 on some AR's.  I know my old Sig 556 had a 1/7 twist which was for heavier bullets.  So mea culpa, I was wrong.

 

Sorry about that.  That's what I get for not checking first to make sure.  So, for that kind of money, I don't think you can go wrong.  I agree it won't be the highest quality, but it will probably work just fine.  Building one is always fun and a good learning experience though.  I just ordered some items to build a 5.56 upper to put on mine as well.

 

 

1:8 is pretty much the standard and what AAC used to make the official BLK round.  But you're right in that there has been a movement since about 2012 to use 1:7 especially as people were shoving 230+ grain projectiles in there.  As long as you don't push the weight limit of projectiles and trying to stablize those projectiles at long distances, 1:8 is fine.  Even if you plan to shoot 220s at a longer than typical distance (100yds) then one should consider 1:7.  Also, some of the projectiles like SMK 240gr are super long which need the extra twist to help stabilze.  If you choose heavy but shorter projectiles 1:8 could be sufficient.  

[Hozzie]

1:8 is pretty much the standard and what AAC used to make the official BLK round.  But you're right in that there has been a movement since about 2012 to use 1:7 especially as people were shoving 230+ grain projectiles in there.  As long as you don't push the weight limit of projectiles and trying to stablize those projectiles at long distances, 1:8 is fine.  Even if you plan to shoot 220s at a longer than typical distance (100yds) then one should consider 1:7.  Also, some of the projectiles like SMK 240gr are super long which need the extra twist to help stabilze.  If you choose heavy but shorter projectiles 1:8 could be sufficient.  

 

Bullet size has been my biggest issue.  I have some 240 grain Missouri Bullet Lead bullets that I use for subsonics (I powdercoat first), but I had a heck of a time getting them to work in my chamber.  I haven't messed with mine in quite a while, but maybe this will prompt me to go out and shoot it some this weekend.  

[Jct1911]

ok, so I notice on the CDNN model, the top rail is removable allowing access to the gas system. Why is this important. Can it not be cleaned without breaking down otherwise?
The Button Rifled barrel type is a new one for me. Just read that this is a progressive cutting method, removing a little more metal with each pass. The CDNN model does not mention rifling method. I'll ask about that as well when I call.

Top rail removable as the "leftover" rails they bought were intended for piston operated guns that LWRC makes. Cleaning a standard gas system is a not a normal thing to do with any frequency.

[MemHeli]

THANK YOU for all the input.

 

Here's what CDNN says about the components used for the build.  Does anyone have experience with CBC barrels?  I do like the fact that the barrel was made in America...but only if it's not crap.  

 

nitride barrel Charleston Barrel Company made in America

creed monarch barrell nut

steel gas block micro .750 low profile gas block

gas tube pistol length gas system

DPMS forward assist

DPMS dust cover

LWRC quad rail

threaded 5/8 x 24 barrel

Edited December 10, 2015 by thesquirrel